1 //===- LowerInvoke.cpp - Eliminate Invoke & Unwind instructions -----------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This transformation is designed for use by code generators which do not yet
11 // support stack unwinding. This pass supports two models of exception handling
12 // lowering, the 'cheap' support and the 'expensive' support.
14 // 'Cheap' exception handling support gives the program the ability to execute
15 // any program which does not "throw an exception", by turning 'invoke'
16 // instructions into calls and by turning 'unwind' instructions into calls to
17 // abort(). If the program does dynamically use the unwind instruction, the
18 // program will print a message then abort.
20 // 'Expensive' exception handling support gives the full exception handling
21 // support to the program at the cost of making the 'invoke' instruction
22 // really expensive. It basically inserts setjmp/longjmp calls to emulate the
23 // exception handling as necessary.
25 // Because the 'expensive' support slows down programs a lot, and EH is only
26 // used for a subset of the programs, it must be specifically enabled by an
29 // Note that after this pass runs the CFG is not entirely accurate (exceptional
30 // control flow edges are not correct anymore) so only very simple things should
31 // be done after the lowerinvoke pass has run (like generation of native code).
32 // This should not be used as a general purpose "my LLVM-to-LLVM pass doesn't
33 // support the invoke instruction yet" lowering pass.
35 //===----------------------------------------------------------------------===//
37 #define DEBUG_TYPE "lowerinvoke"
38 #include "llvm/Transforms/Scalar.h"
39 #include "llvm/Constants.h"
40 #include "llvm/DerivedTypes.h"
41 #include "llvm/Instructions.h"
42 #include "llvm/Module.h"
43 #include "llvm/Pass.h"
44 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
45 #include "llvm/Transforms/Utils/Local.h"
46 #include "llvm/ADT/Statistic.h"
47 #include "llvm/Support/CommandLine.h"
48 #include "llvm/Support/Compiler.h"
49 #include "llvm/Target/TargetLowering.h"
54 STATISTIC(NumInvokes, "Number of invokes replaced");
55 STATISTIC(NumUnwinds, "Number of unwinds replaced");
56 STATISTIC(NumSpilled, "Number of registers live across unwind edges");
58 static cl::opt<bool> ExpensiveEHSupport("enable-correct-eh-support",
59 cl::desc("Make the -lowerinvoke pass insert expensive, but correct, EH code"));
62 class VISIBILITY_HIDDEN LowerInvoke : public FunctionPass {
63 // Used for both models.
67 unsigned AbortMessageLength;
69 // Used for expensive EH support.
71 GlobalVariable *JBListHead;
72 Constant *SetJmpFn, *LongJmpFn;
74 // We peek in TLI to grab the target's jmp_buf size and alignment
75 const TargetLowering *TLI;
78 static char ID; // Pass identification, replacement for typeid
79 explicit LowerInvoke(const TargetLowering *tli = NULL)
80 : FunctionPass((intptr_t)&ID), TLI(tli) { }
81 bool doInitialization(Module &M);
82 bool runOnFunction(Function &F);
84 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
85 // This is a cluster of orthogonal Transforms
86 AU.addPreservedID(PromoteMemoryToRegisterID);
87 AU.addPreservedID(LowerSelectID);
88 AU.addPreservedID(LowerSwitchID);
89 AU.addPreservedID(LowerAllocationsID);
93 void createAbortMessage(Module *M);
94 void writeAbortMessage(Instruction *IB);
95 bool insertCheapEHSupport(Function &F);
96 void splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes);
97 void rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
98 AllocaInst *InvokeNum, SwitchInst *CatchSwitch);
99 bool insertExpensiveEHSupport(Function &F);
102 char LowerInvoke::ID = 0;
103 RegisterPass<LowerInvoke>
104 X("lowerinvoke", "Lower invoke and unwind, for unwindless code generators");
107 const PassInfo *llvm::LowerInvokePassID = X.getPassInfo();
109 // Public Interface To the LowerInvoke pass.
110 FunctionPass *llvm::createLowerInvokePass(const TargetLowering *TLI) {
111 return new LowerInvoke(TLI);
114 // doInitialization - Make sure that there is a prototype for abort in the
116 bool LowerInvoke::doInitialization(Module &M) {
117 const Type *VoidPtrTy = PointerType::get(Type::Int8Ty);
119 if (ExpensiveEHSupport) {
120 // Insert a type for the linked list of jump buffers.
121 unsigned JBSize = TLI ? TLI->getJumpBufSize() : 0;
122 JBSize = JBSize ? JBSize : 200;
123 const Type *JmpBufTy = ArrayType::get(VoidPtrTy, JBSize);
125 { // The type is recursive, so use a type holder.
126 std::vector<const Type*> Elements;
127 Elements.push_back(JmpBufTy);
128 OpaqueType *OT = OpaqueType::get();
129 Elements.push_back(PointerType::get(OT));
130 PATypeHolder JBLType(StructType::get(Elements));
131 OT->refineAbstractTypeTo(JBLType.get()); // Complete the cycle.
132 JBLinkTy = JBLType.get();
133 M.addTypeName("llvm.sjljeh.jmpbufty", JBLinkTy);
136 const Type *PtrJBList = PointerType::get(JBLinkTy);
138 // Now that we've done that, insert the jmpbuf list head global, unless it
140 if (!(JBListHead = M.getGlobalVariable("llvm.sjljeh.jblist", PtrJBList))) {
141 JBListHead = new GlobalVariable(PtrJBList, false,
142 GlobalValue::LinkOnceLinkage,
143 Constant::getNullValue(PtrJBList),
144 "llvm.sjljeh.jblist", &M);
146 SetJmpFn = M.getOrInsertFunction("llvm.setjmp", Type::Int32Ty,
147 PointerType::get(JmpBufTy), (Type *)0);
148 LongJmpFn = M.getOrInsertFunction("llvm.longjmp", Type::VoidTy,
149 PointerType::get(JmpBufTy),
150 Type::Int32Ty, (Type *)0);
153 // We need the 'write' and 'abort' functions for both models.
154 AbortFn = M.getOrInsertFunction("abort", Type::VoidTy, (Type *)0);
155 #if 0 // "write" is Unix-specific.. code is going away soon anyway.
156 WriteFn = M.getOrInsertFunction("write", Type::VoidTy, Type::Int32Ty,
157 VoidPtrTy, Type::Int32Ty, (Type *)0);
164 void LowerInvoke::createAbortMessage(Module *M) {
165 if (ExpensiveEHSupport) {
166 // The abort message for expensive EH support tells the user that the
167 // program 'unwound' without an 'invoke' instruction.
169 ConstantArray::get("ERROR: Exception thrown, but not caught!\n");
170 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
172 GlobalVariable *MsgGV = new GlobalVariable(Msg->getType(), true,
173 GlobalValue::InternalLinkage,
175 std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::Int32Ty));
176 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, &GEPIdx[0], 2);
178 // The abort message for cheap EH support tells the user that EH is not
181 ConstantArray::get("Exception handler needed, but not enabled. Recompile"
182 " program with -enable-correct-eh-support.\n");
183 AbortMessageLength = Msg->getNumOperands()-1; // don't include \0
185 GlobalVariable *MsgGV = new GlobalVariable(Msg->getType(), true,
186 GlobalValue::InternalLinkage,
188 std::vector<Constant*> GEPIdx(2, Constant::getNullValue(Type::Int32Ty));
189 AbortMessage = ConstantExpr::getGetElementPtr(MsgGV, &GEPIdx[0], 2);
194 void LowerInvoke::writeAbortMessage(Instruction *IB) {
196 if (AbortMessage == 0)
197 createAbortMessage(IB->getParent()->getParent()->getParent());
199 // These are the arguments we WANT...
201 Args[0] = ConstantInt::get(Type::Int32Ty, 2);
202 Args[1] = AbortMessage;
203 Args[2] = ConstantInt::get(Type::Int32Ty, AbortMessageLength);
204 (new CallInst(WriteFn, Args, 3, "", IB))->setTailCall();
208 bool LowerInvoke::insertCheapEHSupport(Function &F) {
209 bool Changed = false;
210 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
211 if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
212 std::vector<Value*> CallArgs(II->op_begin()+3, II->op_end());
213 // Insert a normal call instruction...
214 CallInst *NewCall = new CallInst(II->getCalledValue(),
215 CallArgs.begin(), CallArgs.end(), "", II);
216 NewCall->takeName(II);
217 NewCall->setCallingConv(II->getCallingConv());
218 II->replaceAllUsesWith(NewCall);
220 // Insert an unconditional branch to the normal destination.
221 new BranchInst(II->getNormalDest(), II);
223 // Remove any PHI node entries from the exception destination.
224 II->getUnwindDest()->removePredecessor(BB);
226 // Remove the invoke instruction now.
227 BB->getInstList().erase(II);
229 ++NumInvokes; Changed = true;
230 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
231 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
232 writeAbortMessage(UI);
234 // Insert a call to abort()
235 (new CallInst(AbortFn, "", UI))->setTailCall();
237 // Insert a return instruction. This really should be a "barrier", as it
239 new ReturnInst(F.getReturnType() == Type::VoidTy ? 0 :
240 Constant::getNullValue(F.getReturnType()), UI);
242 // Remove the unwind instruction now.
243 BB->getInstList().erase(UI);
245 ++NumUnwinds; Changed = true;
250 /// rewriteExpensiveInvoke - Insert code and hack the function to replace the
251 /// specified invoke instruction with a call.
252 void LowerInvoke::rewriteExpensiveInvoke(InvokeInst *II, unsigned InvokeNo,
253 AllocaInst *InvokeNum,
254 SwitchInst *CatchSwitch) {
255 ConstantInt *InvokeNoC = ConstantInt::get(Type::Int32Ty, InvokeNo);
257 // Insert a store of the invoke num before the invoke and store zero into the
258 // location afterward.
259 new StoreInst(InvokeNoC, InvokeNum, true, II); // volatile
261 BasicBlock::iterator NI = II->getNormalDest()->begin();
262 while (isa<PHINode>(NI)) ++NI;
264 new StoreInst(Constant::getNullValue(Type::Int32Ty), InvokeNum, false, NI);
266 // Add a switch case to our unwind block.
267 CatchSwitch->addCase(InvokeNoC, II->getUnwindDest());
269 // Insert a normal call instruction.
270 std::vector<Value*> CallArgs(II->op_begin()+3, II->op_end());
271 CallInst *NewCall = new CallInst(II->getCalledValue(),
272 CallArgs.begin(), CallArgs.end(), "",
274 NewCall->takeName(II);
275 NewCall->setCallingConv(II->getCallingConv());
276 II->replaceAllUsesWith(NewCall);
278 // Replace the invoke with an uncond branch.
279 new BranchInst(II->getNormalDest(), NewCall->getParent());
280 II->eraseFromParent();
283 /// MarkBlocksLiveIn - Insert BB and all of its predescessors into LiveBBs until
284 /// we reach blocks we've already seen.
285 static void MarkBlocksLiveIn(BasicBlock *BB, std::set<BasicBlock*> &LiveBBs) {
286 if (!LiveBBs.insert(BB).second) return; // already been here.
288 for (pred_iterator PI = pred_begin(BB), E = pred_end(BB); PI != E; ++PI)
289 MarkBlocksLiveIn(*PI, LiveBBs);
292 // First thing we need to do is scan the whole function for values that are
293 // live across unwind edges. Each value that is live across an unwind edge
294 // we spill into a stack location, guaranteeing that there is nothing live
295 // across the unwind edge. This process also splits all critical edges
296 // coming out of invoke's.
298 splitLiveRangesLiveAcrossInvokes(std::vector<InvokeInst*> &Invokes) {
299 // First step, split all critical edges from invoke instructions.
300 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
301 InvokeInst *II = Invokes[i];
302 SplitCriticalEdge(II, 0, this);
303 SplitCriticalEdge(II, 1, this);
304 assert(!isa<PHINode>(II->getNormalDest()) &&
305 !isa<PHINode>(II->getUnwindDest()) &&
306 "critical edge splitting left single entry phi nodes?");
309 Function *F = Invokes.back()->getParent()->getParent();
311 // To avoid having to handle incoming arguments specially, we lower each arg
312 // to a copy instruction in the entry block. This ensures that the argument
313 // value itself cannot be live across the entry block.
314 BasicBlock::iterator AfterAllocaInsertPt = F->begin()->begin();
315 while (isa<AllocaInst>(AfterAllocaInsertPt) &&
316 isa<ConstantInt>(cast<AllocaInst>(AfterAllocaInsertPt)->getArraySize()))
317 ++AfterAllocaInsertPt;
318 for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end();
320 // This is always a no-op cast because we're casting AI to AI->getType() so
321 // src and destination types are identical. BitCast is the only possibility.
322 CastInst *NC = new BitCastInst(
323 AI, AI->getType(), AI->getName()+".tmp", AfterAllocaInsertPt);
324 AI->replaceAllUsesWith(NC);
325 // Normally its is forbidden to replace a CastInst's operand because it
326 // could cause the opcode to reflect an illegal conversion. However, we're
327 // replacing it here with the same value it was constructed with to simply
329 NC->setOperand(0, AI);
332 // Finally, scan the code looking for instructions with bad live ranges.
333 for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB)
334 for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E; ++II) {
335 // Ignore obvious cases we don't have to handle. In particular, most
336 // instructions either have no uses or only have a single use inside the
337 // current block. Ignore them quickly.
338 Instruction *Inst = II;
339 if (Inst->use_empty()) continue;
340 if (Inst->hasOneUse() &&
341 cast<Instruction>(Inst->use_back())->getParent() == BB &&
342 !isa<PHINode>(Inst->use_back())) continue;
344 // If this is an alloca in the entry block, it's not a real register
346 if (AllocaInst *AI = dyn_cast<AllocaInst>(Inst))
347 if (isa<ConstantInt>(AI->getArraySize()) && BB == F->begin())
350 // Avoid iterator invalidation by copying users to a temporary vector.
351 std::vector<Instruction*> Users;
352 for (Value::use_iterator UI = Inst->use_begin(), E = Inst->use_end();
354 Instruction *User = cast<Instruction>(*UI);
355 if (User->getParent() != BB || isa<PHINode>(User))
356 Users.push_back(User);
359 // Scan all of the uses and see if the live range is live across an unwind
360 // edge. If we find a use live across an invoke edge, create an alloca
361 // and spill the value.
362 std::set<InvokeInst*> InvokesWithStoreInserted;
364 // Find all of the blocks that this value is live in.
365 std::set<BasicBlock*> LiveBBs;
366 LiveBBs.insert(Inst->getParent());
367 while (!Users.empty()) {
368 Instruction *U = Users.back();
371 if (!isa<PHINode>(U)) {
372 MarkBlocksLiveIn(U->getParent(), LiveBBs);
374 // Uses for a PHI node occur in their predecessor block.
375 PHINode *PN = cast<PHINode>(U);
376 for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i)
377 if (PN->getIncomingValue(i) == Inst)
378 MarkBlocksLiveIn(PN->getIncomingBlock(i), LiveBBs);
382 // Now that we know all of the blocks that this thing is live in, see if
383 // it includes any of the unwind locations.
384 bool NeedsSpill = false;
385 for (unsigned i = 0, e = Invokes.size(); i != e; ++i) {
386 BasicBlock *UnwindBlock = Invokes[i]->getUnwindDest();
387 if (UnwindBlock != BB && LiveBBs.count(UnwindBlock)) {
392 // If we decided we need a spill, do it.
395 DemoteRegToStack(*Inst, true);
400 bool LowerInvoke::insertExpensiveEHSupport(Function &F) {
401 std::vector<ReturnInst*> Returns;
402 std::vector<UnwindInst*> Unwinds;
403 std::vector<InvokeInst*> Invokes;
405 for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB)
406 if (ReturnInst *RI = dyn_cast<ReturnInst>(BB->getTerminator())) {
407 // Remember all return instructions in case we insert an invoke into this
409 Returns.push_back(RI);
410 } else if (InvokeInst *II = dyn_cast<InvokeInst>(BB->getTerminator())) {
411 Invokes.push_back(II);
412 } else if (UnwindInst *UI = dyn_cast<UnwindInst>(BB->getTerminator())) {
413 Unwinds.push_back(UI);
416 if (Unwinds.empty() && Invokes.empty()) return false;
418 NumInvokes += Invokes.size();
419 NumUnwinds += Unwinds.size();
421 // TODO: This is not an optimal way to do this. In particular, this always
422 // inserts setjmp calls into the entries of functions with invoke instructions
423 // even though there are possibly paths through the function that do not
424 // execute any invokes. In particular, for functions with early exits, e.g.
425 // the 'addMove' method in hexxagon, it would be nice to not have to do the
426 // setjmp stuff on the early exit path. This requires a bit of dataflow, but
427 // would not be too hard to do.
429 // If we have an invoke instruction, insert a setjmp that dominates all
430 // invokes. After the setjmp, use a cond branch that goes to the original
431 // code path on zero, and to a designated 'catch' block of nonzero.
432 Value *OldJmpBufPtr = 0;
433 if (!Invokes.empty()) {
434 // First thing we need to do is scan the whole function for values that are
435 // live across unwind edges. Each value that is live across an unwind edge
436 // we spill into a stack location, guaranteeing that there is nothing live
437 // across the unwind edge. This process also splits all critical edges
438 // coming out of invoke's.
439 splitLiveRangesLiveAcrossInvokes(Invokes);
441 BasicBlock *EntryBB = F.begin();
443 // Create an alloca for the incoming jump buffer ptr and the new jump buffer
444 // that needs to be restored on all exits from the function. This is an
445 // alloca because the value needs to be live across invokes.
446 unsigned Align = TLI ? TLI->getJumpBufAlignment() : 0;
448 new AllocaInst(JBLinkTy, 0, Align, "jblink", F.begin()->begin());
450 std::vector<Value*> Idx;
451 Idx.push_back(Constant::getNullValue(Type::Int32Ty));
452 Idx.push_back(ConstantInt::get(Type::Int32Ty, 1));
453 OldJmpBufPtr = new GetElementPtrInst(JmpBuf, &Idx[0], 2, "OldBuf",
454 EntryBB->getTerminator());
456 // Copy the JBListHead to the alloca.
457 Value *OldBuf = new LoadInst(JBListHead, "oldjmpbufptr", true,
458 EntryBB->getTerminator());
459 new StoreInst(OldBuf, OldJmpBufPtr, true, EntryBB->getTerminator());
461 // Add the new jumpbuf to the list.
462 new StoreInst(JmpBuf, JBListHead, true, EntryBB->getTerminator());
464 // Create the catch block. The catch block is basically a big switch
465 // statement that goes to all of the invoke catch blocks.
466 BasicBlock *CatchBB = new BasicBlock("setjmp.catch", &F);
468 // Create an alloca which keeps track of which invoke is currently
469 // executing. For normal calls it contains zero.
470 AllocaInst *InvokeNum = new AllocaInst(Type::Int32Ty, 0, "invokenum",
472 new StoreInst(ConstantInt::get(Type::Int32Ty, 0), InvokeNum, true,
473 EntryBB->getTerminator());
475 // Insert a load in the Catch block, and a switch on its value. By default,
476 // we go to a block that just does an unwind (which is the correct action
477 // for a standard call).
478 BasicBlock *UnwindBB = new BasicBlock("unwindbb", &F);
479 Unwinds.push_back(new UnwindInst(UnwindBB));
481 Value *CatchLoad = new LoadInst(InvokeNum, "invoke.num", true, CatchBB);
482 SwitchInst *CatchSwitch =
483 new SwitchInst(CatchLoad, UnwindBB, Invokes.size(), CatchBB);
485 // Now that things are set up, insert the setjmp call itself.
487 // Split the entry block to insert the conditional branch for the setjmp.
488 BasicBlock *ContBlock = EntryBB->splitBasicBlock(EntryBB->getTerminator(),
491 Idx[1] = ConstantInt::get(Type::Int32Ty, 0);
492 Value *JmpBufPtr = new GetElementPtrInst(JmpBuf, &Idx[0], Idx.size(),
494 EntryBB->getTerminator());
495 Value *SJRet = new CallInst(SetJmpFn, JmpBufPtr, "sjret",
496 EntryBB->getTerminator());
498 // Compare the return value to zero.
499 Value *IsNormal = new ICmpInst(ICmpInst::ICMP_EQ, SJRet,
500 Constant::getNullValue(SJRet->getType()),
501 "notunwind", EntryBB->getTerminator());
502 // Nuke the uncond branch.
503 EntryBB->getTerminator()->eraseFromParent();
505 // Put in a new condbranch in its place.
506 new BranchInst(ContBlock, CatchBB, IsNormal, EntryBB);
508 // At this point, we are all set up, rewrite each invoke instruction.
509 for (unsigned i = 0, e = Invokes.size(); i != e; ++i)
510 rewriteExpensiveInvoke(Invokes[i], i+1, InvokeNum, CatchSwitch);
513 // We know that there is at least one unwind.
515 // Create three new blocks, the block to load the jmpbuf ptr and compare
516 // against null, the block to do the longjmp, and the error block for if it
517 // is null. Add them at the end of the function because they are not hot.
518 BasicBlock *UnwindHandler = new BasicBlock("dounwind", &F);
519 BasicBlock *UnwindBlock = new BasicBlock("unwind", &F);
520 BasicBlock *TermBlock = new BasicBlock("unwinderror", &F);
522 // If this function contains an invoke, restore the old jumpbuf ptr.
525 // Before the return, insert a copy from the saved value to the new value.
526 BufPtr = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", UnwindHandler);
527 new StoreInst(BufPtr, JBListHead, UnwindHandler);
529 BufPtr = new LoadInst(JBListHead, "ehlist", UnwindHandler);
532 // Load the JBList, if it's null, then there was no catch!
533 Value *NotNull = new ICmpInst(ICmpInst::ICMP_NE, BufPtr,
534 Constant::getNullValue(BufPtr->getType()),
535 "notnull", UnwindHandler);
536 new BranchInst(UnwindBlock, TermBlock, NotNull, UnwindHandler);
538 // Create the block to do the longjmp.
539 // Get a pointer to the jmpbuf and longjmp.
540 std::vector<Value*> Idx;
541 Idx.push_back(Constant::getNullValue(Type::Int32Ty));
542 Idx.push_back(ConstantInt::get(Type::Int32Ty, 0));
543 Idx[0] = new GetElementPtrInst(BufPtr, &Idx[0], 2, "JmpBuf", UnwindBlock);
544 Idx[1] = ConstantInt::get(Type::Int32Ty, 1);
545 new CallInst(LongJmpFn, Idx.begin(), Idx.end(), "", UnwindBlock);
546 new UnreachableInst(UnwindBlock);
548 // Set up the term block ("throw without a catch").
549 new UnreachableInst(TermBlock);
551 // Insert a new call to write(2, AbortMessage, AbortMessageLength);
552 writeAbortMessage(TermBlock->getTerminator());
554 // Insert a call to abort()
555 (new CallInst(AbortFn, "",
556 TermBlock->getTerminator()))->setTailCall();
559 // Replace all unwinds with a branch to the unwind handler.
560 for (unsigned i = 0, e = Unwinds.size(); i != e; ++i) {
561 new BranchInst(UnwindHandler, Unwinds[i]);
562 Unwinds[i]->eraseFromParent();
565 // Finally, for any returns from this function, if this function contains an
566 // invoke, restore the old jmpbuf pointer to its input value.
568 for (unsigned i = 0, e = Returns.size(); i != e; ++i) {
569 ReturnInst *R = Returns[i];
571 // Before the return, insert a copy from the saved value to the new value.
572 Value *OldBuf = new LoadInst(OldJmpBufPtr, "oldjmpbufptr", true, R);
573 new StoreInst(OldBuf, JBListHead, true, R);
580 bool LowerInvoke::runOnFunction(Function &F) {
581 if (ExpensiveEHSupport)
582 return insertExpensiveEHSupport(F);
584 return insertCheapEHSupport(F);